As a National RSB Resource, the Ligand Assay and Analysis Core will serve an essential role in this U54 Center, and other RSB-supported Centers. First, the Core will provide high quality, cost effective assay services. Second, develop new state-of-the-art assay methods to accommodate investigator needs. Third, the Core will provide assistance and consultation regarding assay methodology, data reduction/analysis, data interpretation and biomathematical modeling. The accurate, precise and dependable measurement of reproductive hormones is an essential component in the mission of Ligand Core. The justification for establishing a Core facility relates to the savings in cost, resources and personnel to internal and external RSB-supported investigators, as they will not need to develop and maintain these methods in each individual laboratory. The technical expertise and equipment required to perform high volume or diverse testing by each investigator would be inefficient and divert effort and resources from important research questions. Also, a central Core facility can implement uniform standards for assay performance, quality controls and data reduction. The implementation of new methods or enhancement of current methods require technical expertise that would be costly and inefficient to establish in-house by each project investigator. One of the major rationales for establishing the Core is to provide state of the art assay services in a cost efficient manner. This mission will include development of assays with enhanced sensitivity and specificity, transferring methods from radioactive to nonradioactive systems, implementation of automation equipment (for high volume tests). Assay automation can enhance assay performance by improving assay precision and reducing costs by increasing the number of tests that can be performed by the technologist. Finally, providing services to other RSB-supported Centers and other reproductive scientists within the University of Virginia, promote a spirit of cooperation that may lead to future collaborations between investigators.